The present invention relates to an improvement in a sheet alignment device for an automatic duplex unit provided in a copying apparatus which copies a document image onto both sides of a recording sheet.
As a device for reversing a document and thereby copying from both sides of the document, there has been known a reversible automatic document feeder (hereinafter referred to as RADF). When such a device is used, a large number of copies can be easily produced. Further, copies produced are in the same sequence as that of the documents, which eliminates the necessity of changing the sequence of produced copies.
Further, when interlocked with a sorter, collating and sorting by page can be automatically conducted and a large number of copies can be accurately put in order.
As a device in which copies are automatically produced on both sides of a recording sheet through a single operation of a button, an automatic duplex unit (hereinafter referred to as an ADU) is known. When this unit is used, information on both sides of a document is copied onto both sides of a recording sheet, which results in reducing the cost of recording sheets and making it possible to file recorded sheets easily. Further, it can be applied in many ways, including collecting materials in a booklet form.
In the case of duplex copying described above, a recording sheet, onto the first side of which a document image has been copied, is reversed and stacked on a stacker, and then another document image is copied onto the second side of the recording sheet.
A sheet alignment device is provided on the width sides of the stacker in order to align the recording sheets.
The sheet alignment device has a home position where the sheet alignment device is set to a width wider than that of the maximum applicable recording sheet size(for example, A3 size).
Just before the copying operation is started, the recording sheet size is determined automatically or manually, and the width of the sheet alignment device is controlled in accordance with the aforementioned recording sheet size. After the recording sheet size has been determined in the manner described above, a pushing member is moved to the corresponding position by a step motor or other drive units.
However, in the case described above, it takes some time to control the width of the sheet alignment device so that the pushing member is moved from the home position (the maximum width) to the position which agrees with the recording sheet size (for example, A4 size) being utilized. For this reason, the start of the copying operation is delayed and the productivity of duplex copying can not be improved.